**7. Operative techniques for carotid endarterectomy**

Patients with symptomatic carotid stenosis >50% or asymptomatic carotid stenosis >70%, or who had a stroke ipsilateral to the carotid stenosis while on best medical management should be offered a carotid revascularization procedure. CEA remains the gold standard of care for carotid stenosis. It should be considered for those patients who have a low medical risk for general anesthesia, have not had prior radical neck surgery or radiation to the neck and who have a surgically accessible carotid bifurcation.

Because the surgery involves clamping the carotid artery temporarily, some surgeons will decide to place a silicone tubing to shunt the blood and allow continuous carotid flow throughout the operation, however, this can be associated with a higher rate of thromboem‐ bolic events and some surgeons will choose to place a shunt in only select cases [40,41]. If the surgeon chooses to selectively shunt only those patients who do not tolerate carotid clamping for the surgery, he or she can decide to perform this surgery either awake under local anesthesia allowing for intra-operative neurological exams or under general anesthesia with neuromo‐ nitoring to evaluate for changes in somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) while the carotid artery is clamped. If the surgeon chooses to shunt all carotids, then the routine use of neuromonitoring would not typically be required or justified. Some surgeons will measure stump pressures from the external carotid artery (ECA) after clamping to help determine if the patient will require selective placement of a carotid shunt, however, this has not been shown to be a good predictor of whether a patient will go on to have a stroke from the surgery. The authors here routinely use neuromonitoring for all patients under general anesthesia in order to choose the patients who will require selective shunting.

Pre-operative medical preparation is important, and patients undergoing CEA should be taking an anti-platelet such as aspirin daily. The use of clopidogrel, although not required, would not necessarily prevent the surgeon from performing the CEA, although there is a slightly higher risk of local hematoma for patients taking combination anti-platelet agents. A drain is often recommended in selected cases, particularly if the patient is taking both aspirin and clopidogrel at the time of the surgery, and if it is difficult to maintain a dry surgical field at the time of the operation.

the occurrence of restenosis >70% in the angioplasty alone group compared to the stent group was more than twice as frequent (36.2% vs 16.6%, p=0.04). Of all patients with >70% restenosis in the first year after treatment with CEA or CAS compared to the patients with <70% restenosis in this same time period, there was a trend toward a higher ipsilateral stroke rate in the greater stenosis group, but this result did not reach clinical significance (9.7% vs 5.4%, p=0.4) [33]. These results suggest that CEA provides the greatest durability of treatment with fewer cases of hemodynamically significant recurrent stenosis compared with stent placement, although stent placement is significantly superior to angioplasty alone for long-term durability. Treated patients should be followed for recurrent stenosis, and although the greater stenosis group did not have a statistically significant increase in the number of ipsilateral stroke events, it would be wise to more closely monitor these patients, be more aggressive with medical management with anti-platelet agents, or even offer repeat treatment for those patients with progressively

Patients with symptomatic carotid stenosis >50% or asymptomatic carotid stenosis >70%, or who had a stroke ipsilateral to the carotid stenosis while on best medical management should be offered a carotid revascularization procedure. CEA remains the gold standard of care for carotid stenosis. It should be considered for those patients who have a low medical risk for general anesthesia, have not had prior radical neck surgery or radiation to the neck and who

Because the surgery involves clamping the carotid artery temporarily, some surgeons will decide to place a silicone tubing to shunt the blood and allow continuous carotid flow throughout the operation, however, this can be associated with a higher rate of thromboem‐ bolic events and some surgeons will choose to place a shunt in only select cases [40,41]. If the surgeon chooses to selectively shunt only those patients who do not tolerate carotid clamping for the surgery, he or she can decide to perform this surgery either awake under local anesthesia allowing for intra-operative neurological exams or under general anesthesia with neuromo‐ nitoring to evaluate for changes in somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) while the carotid artery is clamped. If the surgeon chooses to shunt all carotids, then the routine use of neuromonitoring would not typically be required or justified. Some surgeons will measure stump pressures from the external carotid artery (ECA) after clamping to help determine if the patient will require selective placement of a carotid shunt, however, this has not been shown to be a good predictor of whether a patient will go on to have a stroke from the surgery. The authors here routinely use neuromonitoring for all patients under general anesthesia in order to choose the patients who will require selective shunting.

Pre-operative medical preparation is important, and patients undergoing CEA should be taking an anti-platelet such as aspirin daily. The use of clopidogrel, although not required, would not necessarily prevent the surgeon from performing the CEA, although there is a slightly higher risk of local hematoma for patients taking combination anti-platelet agents. A

worsening stenosis during the follow up period.

212 Carotid Artery Disease - From Bench to Bedside and Beyond

have a surgically accessible carotid bifurcation.

**7. Operative techniques for carotid endarterectomy**

The approach to the carotid sheath for the CEA begins with positioning the patient in the supine position on the operating table with the head turned slightly toward the contralateral side and the neck slightly extended for optimum exposure. The planned incision line should be marked with a skin marker along the anterior border of the sternocleidomastoid muscle, which would be approximately parallel to the expected course of the carotid artery, for optimum exposure. The neck should be prepped behind and below the ear from just above the mastoid down to the upper chest, just below the clavicle, and from midline out laterally to the anterolateral border of the trapezius muscle above the shoulder. After proper sterile technique for preparation and draping of the operative field, the skin is incised along the previously marked incision site. The platysma muscle is encountered and split parallel to the muscle fibers, which is also parallel to the incision. The omohyoid muscle is separated as needed for adequate exposure of the common carotid artery (CCA) and at least 2-3cm of the ECA and internal carotid artery (ICA). If additional exposure is required superiorly, the superior aspect of the planned incision should be extended superiorly and posteriorly just below the mastoid, and care should be taken to not injure the hypoglossal nerve at this level during the deeper dissection. Care should be taken to avoid injury to the recurrent laryngeal nerve or the esophagus during the dissection to the carotid sheath. The carotid artery typically resides medially in the carotid sheath, the internal jugular vein typically lies lateral to the carotid artery, and the vagus nerve typically lies deep to both of these structures and between them.

The systolic blood pressure (SBP) is raised prior to placing the clamp, typically to 140-160 mmHg for patients who are normotensive at baseline, to help promote perfusion through collateral circulation. Generally, raising the SBP by about 20% of the baseline should allow for adequate collateral circulation. The carotid artery is then clamped in the following order when the surgeon is ready to perform the endarterectomy, with the ICA being clamped first followed by the CCA (typically with a Fogarty carotid clamp or other atraumatic clamp device), followed by the ECA. If neuromonitoring is used, these signals are also monitored continuously, and changes in the SSEP and or MEP signals that would be consistent with ischemia changes should prompt the surgeon to selectively place a shunt into that carotid artery.

The arteriotomy is performed with a #11 scalpel blade until a pair of Potts scissors can be inserted into the true lumen and the incision can be extended from the CCA to the ICA full thickness through the plaque. Care must be taken to identify the superior thyroid artery origin, especially if there is back-bleeding after performing the arteriotomy, as this may arise very near the carotid bifurcation, unless a temporary clip is applied to this arterial branch. The plaque is then carefully but quickly teased from the endothelial layer of the carotid artery and the plaque is transected as far as possible with the exposure and the carotid artery wall is inspected for loose debris which is carefully removed and irrigated with heparinized saline. The carotid artery is then sutured with 6-0 prolene in simple running fashion, using a minimal full thickness stitch to reapproximate the incised vessel edges without causing additional stenosis with the suturing. Multiple simple interrupted sutures can also be used, but this tends to be significantly more time consuming and is no more effective than the simple running suture. The use of heparinized saline throughout the procedure and back bleeding from the ECA to flush out any loose particles just prior to placing the last 6-0 prolene suture into the carotid artery is also recommended. The clamps are then removed in the reverse order that they were placed, with the ECA clamp removed first, followed by the CCA clamp, followed lastly by the ICA clamp. There are several standard techniques to close a cervical approach incision, which would typically include a subcutaneous layer of absorbable suture placed in inverted simple interrupted fashion followed by a cosmetic skin edge reapproximation with absorbable running subcuticular sutures, sterile adhesive strips or skin glue.

followed by a continuous drip of 0.125mcg/kg/min to a maximum of 10mcg/min for 24h, and then followed by 325mg aspirin and 75mg clopidogrel daily for 3 months before the next follow up angiogram. At the time of the follow up angiogram, if there is no in-stent stenosis or other reason for additional procedures, then the clopidogrel can be stopped, and the patient is

Management of Atherosclerotic Carotid Artery Stenosis

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One potential complication with stent placement is thromboembolic events that have been found to occur in up to 10% of cases where the patient was found to not have adequate platelet inhibition with the standard anti-platelet therapy described above, and these individuals are described as "non-responders" [42]. It is now known that the incidence of non-responders to clopidogrel is potentially very high, ranging from 5-40% of treated patients, and appears to be more prevalent in the Asian population compared with the Caucasian or African populations. Clopidogrel is a pro-drug that is metabolized by the cytochrome P450 emzyme pathway in the liver into the active thiol metabolite. Factors such as platelet ADP receptor heterogeneity, poor drug absorption, drug-drug interactions, and differences in metabolism of the drug by the cytochrome P450 system, as well as patient non-compliance may all contribute to the variability of drug efficacy between individuals. Variant alleles of the CYP2C19 and CYP2C9 enzymes (CYP2C19 I331V, CYP2C9 R144C and CYP2C9 I359L) have been described to have a reduced conversion rate of the clopidogrel pro-drug into the active thiol metabolite [43]. Alternative anti-platelet agents such as prasugrel (Effient) may be used, as non-responders to clopidogrel typically will respond adequately to prasugrel. Other alternative anti-platelet agents should be evaluated with the most current pharmacological literature. A pharmacy consultation may be needed to find an effective alternative anti-platelet drug for patients who do not respond to a therapeutic level with these medications. It would be wise to test all patients who require elective pre-medication with aspirin and clopidogrel using a P2Y12 activity test before performing the procedure, whenever possible, in order to identify those patients who may be

The patient is placed in the supine position on the angiography table with the femoral artery access site prepared in the usual sterile fashion. Using the modified Seldinger technique, the femoral artery is accessed with a long access catheter typically with at least a 6F inner diameter (ID) to allow room for placement of a distal protection device and the stent device simultane‐ ously, along with any additional 0.014 or 0.018 inch microwires, termed "buddy wires," which may be placed to improve the stability of the guide catheter in the CCA. The guide catheter is positioned in the CCA just proximal to the carotid bifurcation and appropriate digital sub‐ traction angiography (DSA) is performed to optimally visualize the stenosis and the takeoff of the ICA. A 0.014 inch microwire is guided beyond the ICA stenosis using a road map. The distal protection device is deployed over the microwire into a straight segment of the ICA proximal to the petrous segment. Occasionally, the stenosis will be so severe that pre-dilation angioplasty of the stenosis with a balloon that has a low crossing profile, such as a 2.5mm x 30mm Maverick or Mini-Trek balloon, before the placement of the distal protection device or the stent may be required. Cardiovascular instability or arrhythmias are uncommon when inflating a small balloon such as this at the ICA origin. An appropriately sized stent is selected, which is typically about 30-40mm in length to cover the lesion completely and about 1-2mm

continued on low-dose aspirin 81mg daily indefinitely.

non-responders to the standard therapy.
